For filling containers with liquid products filling machines known as volumetric filling machines already exist. Such machines comprise a revolving platform on which containers to be filled are carried one behind the other, suitably spaced from each other. Containers entering the filling cycle are clamped on to the platform by filling devices which form part of the machine and which are supported above the revolving platform. These devices form part of the product dosage and delivery units which are equiangularly spaced from one another and fixed to a second revolving platform connected to the first. The number of such units is established during the design phase of the machine and each unit includes a dosage apparatus which effects dosage of the product using a double-acting piston connected, by means of a control and distribution valve (normally of the slide type), to the feed source of the product, according to the capacity of the containers to be filled, and a delivery apparatus having a nozzle which can be positioned in the mouth of a container and connected to the outlet of the control and distribution valve of the dosage apparatus.
The dosage of the apparatus may be controlled according to a well known technique, by various means, e.g. controlling, with detection devices, the stroke of the piston of the dosage device. U.S. Pat. No. 3,870,089 describes a filling machine, of the type with which the present invention is concerned, in which a number of dosage apparatuses are fixed to a first platform, each apparatus having a piston whose rod is extended vertically upwards away from the surface of the platform on which the containers to be filled are carried. The delivery apparatuses are supported by the second platform and connected to the dosage apparatuses by corresponding product control and distribution valves fixed to the first platform. The second platform is rotated by a first drive means and causes rotation of the first platform.
Between the first and second platforms a disc of adjustable height in relation to the first platform is positioned. The disc supports a series of microswitches, equal in number to the number of dosage apparatuses, arranged in such a way that they can be operated by a striker connected to the piston rod of each dosage apparatus. These microswitches, when activated, cause operation of the control and distribution valves to which the dosage apparatuses are connected to expel the product from one part or from the other of the chambers in which the pistons of the dosage apparatuses slide, the parts of the chamber being at opposite sides of the piston. Depending on the height of the disc relative to the first platform, there is a desired stroke of the piston inside the relative chambers and therefore a different volumetric dosage of the product to be sent to the delivery apparatuses. Excellent results have been achieved with machines of this type as regards dosage of the product and operative speed; however, it has been noticed that such machines do not lend themselves to variations in the number of operative apparatuses and furthermore that for attention to a dosage apparatus or a delivery apparatus, it is necessary to stop the machine for the whole length of time required for the resetting of functioning conditions of the apparatus which is being attended to.